Spread-spectrum communication is so arranged that the transmitter side transmits information by spreading the transmission spectrum (band expansion) using a PN code (maximal sequence code of code length 127, for example) with a much higher speed than the information and that a receiver side correlates the received signal with a PN code in its own receiver to demodulate data. This system has an advantage, among others, that deterioration of the received signal caused by frequency selective fading can be reduced.
Such a spread-spectrum communication receiver used in communication of this type is disclosed, for example, in Japanese Patent Publication No. 59-186440A. As shown in FIG. 5, this receiver essentially consists of matched filters 1 and 2, phase shifter 3 and phase detector 4, and is configured to apply a received spread-spectrum signal S to matched filters 1' and 2' to correlate it with a receiver's code and obtain output signals A and B. The output signal B is phase-shifted by 90.degree. in phase shifter 3, and the phase shifted output signal B' and the output signal A are applied to the phase detector 4 to demodulate a data signal D.
In the conventional spread-spectrum communication receiver, however, the phase shifter, because of its position at the output side of the matched filter, must shift the phase of an output signal of a wideband, and it is therefore required to be a wideband phase shifter. Further, the wider the spread-out band, the wider is the required bandwidth of the phase shifter, and it is also required to uniformly shift the phase in this band. However, it is difficult to realize a phase shifter satisfying these requirements. Beside this, the phase shifter must be able to control the phase in order to correct a phase deviation practically caused by varieties in the characteristics of elements, varieties in the wiring length, temperature variations, etc. However, it is very difficult to realize such an arrangement over a wide band.
Assuming that the phase shifter is configured for phase controls as indicated above to automatically adjust a phase deviation, since the input signal to the correlator is a spread-spectrum signal, the output of the correlator is a correlated spike-waveform signal having a narrow time width, and a control circuit for processing the signal is complicated accordingly.